well loggining. gamma ray log
TRANSCRIPT
Lab. 1 : Well logging principles
Well planning and execution
Lab. 1 : Well logging principles
Aim of well logging
Evaluation of subsurface hydrocarbon accumulations
Gas
Oil
Water
Lab. 1 : Well logging principles
Hydrocarbon Traps
• Structural
•Stratigraphic
•Mixed
Lab. 1 : Well logging principles
Petroleum System Processes
24803
Petroleum System ElementsPetroleum System Elements
120° F120° F
350° F350° FGenerationGeneration
MigrationMigration
Seal RockSeal Rock
Reservoir RockReservoir Rock
OilOil
WaterWater
Gas CapGas Cap
EntrapmentEntrapment
Lab. 1 : Well logging principles
Lab. 1 : Well logging principles
What is a log?
Well log is a continuous record of measurementmade in bore hole that respond to variation insome physical properties of rocks through whichthe bore hole is drilled.
Lab. 1 : Well logging principles
Log acquisition
Lab. 1 : Well logging principles
Log acquisition – types of logs
• Geophysical Logs– Gamma Ray
– Resistivity
– Sonic
– Neutron
– Density
– Dip Meter
– Borehole Imaging
• Production Logging– Pressure
– Temperature
– Spinner
– Fluid Density
• Well Inspection– Caliper
– Electro-magnetic
– Ultrasonic
– RA Tracer
– Video
Lab. 1 : Well logging principles
Lab. 1 : Well logging principles
Lab. 1 : Well logging principlesThe borehole environment
Lithology Logs
Gamma Ray
• Measures Natural radioactivity
• Main radioactive elements:
– Potassium
– Thorium
– Uranium
• K and TH mostly in shales
U from other sources
• Primary use a a basic lithology
indicator (sand/shale)
Lab. 1 : Gamma Ray log1- Records radioactivity of a formation2- Shales have high gamma radioactive response3- Gamma ray logs are most commonly used logs for sequence stratigraphic analysis.4- Gamma Rays are high-energy electromagnetic waves which are emitted by atomic nuclei as a form of radiation.5- Gamma ray log is measurement of natural radioactivity in formation versus depth.6- It measures the radiation emitting from naturally occurring U, Th, and K.7- It is also known as shale log.8- GR log reflects shale or clay content.9- Clean formations have low radioactivity level.
• Correlation between wells,• Determination of bed boundaries,• Evaluation of shale content within a formation,• Mineral analysis,GR log can be run in both open and cased hole
All rocks contain some radioactive material, although marine shales have a higher gamma ray emission level than sandstone, limestone and dolomite. This difference makes the gamma ray log especially useful for distinguishing shales from non shales, therefore the gamma ray is essentially a lithology log.
Shale volume
Shale
Sand
Shale
Shale
Sand
1) Pick a clean GR response
GR 90 -> Vsh = 55%
0 150api
2) Pick a shale GR response
3) Scale between
35
90
GR log - Gr clean
Vsh =
GR shale - Gr clean
135
Lab. 1 : Well logging principles
Lab. 1 : Well logging principles
Lab. 1 : Well logging principles
Lab. 1 : Well logging principles
Lab. 1 : Well logging principles